The present invention concerns optical spectrum analysis and pertains particularly to the graphical presentation of spectral information for aid in compliance measurements.
Wavelength division multiplexing (WDM) fiber optic transmission systems currently utilize hundreds of laser signals to transmit information. Each laser signal resides within a specific frequency channel, defined by its center frequency and signal power. It is desirable to measure the frequency and power at various times in the manufacture, deployment and operation of a WDM system.
Channel analyzer instruments, such as optical spectrum analyzers and multiwavelength meters, can display a spectrum of WDM channels in a linear fashion across the instrument display. The horizontal (x) axis usually shows frequency; the vertical (y) axis power.
The user can “scan” the x-axis of the display to look at a particular signal, or set of signals. The user can also narrow the field of view and “zoom in” on specific wavelengths. Alternatively, a tabular listing of the wavelengths and the corresponding optical powers can be presented.
When there are few channels present, the user can see the spectral shape of individual signals. In this low-channel case, the user tabular results are less frequently used. As channel counts increase, the channels get compressed in the x-axis making it more difficult for the user to identify the spectral shape of the channels AND the user is forced to tediously scan and zoom-in to get spectral information on individual channels. In these high-channel count cases, the user tends to rely more on the tabular channel information and give up the visual information.
The tabular data is also becoming more difficult to navigate as it increases to multiple pages. The tabular data can be analyzed using an external computer to assess the performance of the individual laser signals relative to the channel center frequency, minimum and maximum power and frequency constraints. However, this is complicated because it requires the user to develop additional software.